std::forward_list::forward_list

(1) empty container constructor (default constructor)

Constructs an empty container, with no elements.

(2) fill constructor

Constructs a container with n elements. Each element is a copy of val (if provided).

(3) range constructor

Constructs a container with as many elements as the range [first,last), with each element emplace-constructed from its corresponding element in that range, in the same order.

(4) copy constructor (and copying with allocator)

Constructs a container with a copy of each of the elements in fwdlst, in the same order.

(5) move constructor (and moving with allocator)

Constructs a container that acquires the elements of fwdlst.
If alloc is specified and is different from fwdlst's allocator, the elements are moved. Otherwise, no elements are constructed (their ownership is directly transferred).
fwdlst is left in an unspecified but valid state.

(6) initializer list constructor

Constructs a container with a copy of each of the elements in il, in the same order.

Parameters

alloc

Allocator object.
The container keeps and uses an internal copy of this allocator.
Member type allocator_type is the internal allocator type used by the container, defined in forward_list as an alias of its second template parameter (Alloc).
If allocator_type is an instantiation of the default allocator (which has no state), this is not relevant.

n

Initial container size (i.e., the number of elements in the container at construction).
Member type size_type is an unsigned integral type.

val

Value to fill the container with. Each of the n elements in the container is initialized to a copy of this value.
Member type value_type is the type of the elements in the container, defined in forward_list as an alias of its first template parameter (T).

first, last

Input iterators to the initial and final positions in a range. The range used is [first,last), which includes all the elements between first and last, including the element pointed by first but not the element pointed by last.
The function template argument InputIterator shall be an input iterator type that points to elements of a type from which value_type objects can be constructed.

fwdlst

Another forward_list object of the same type (with the same class template arguments), whose contents are either copied or acquired.

il

An initializer_list object.
These objects are automatically constructed from initializer list declarators.
Member type value_type is the type of the elements in the container, defined in forward_list as an alias of its first template parameter (T).

Example

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// forward_list constructors
#include <iostream>
#include <forward_list>

int main ()
{
  // constructors used in the same order as described above:

  std::forward_list<int> first;                      // default: empty
  std::forward_list<int> second (3,77);              // fill: 3 seventy-sevens
  std::forward_list<int> third (second.begin(), second.end()); // range initialization
  std::forward_list<int> fourth (third);            // copy constructor
  std::forward_list<int> fifth (std::move(fourth));  // move ctor. (fourth wasted)
  std::forward_list<int> sixth = {3, 52, 25, 90};    // initializer_list constructor

  std::cout << "first:" ; for (int& x: first)  std::cout << " " << x; std::cout << '\n';
  std::cout << "second:"; for (int& x: second) std::cout << " " << x; std::cout << '\n';
  std::cout << "third:";  for (int& x: third)  std::cout << " " << x; std::cout << '\n';
  std::cout << "fourth:"; for (int& x: fourth) std::cout << " " << x; std::cout << '\n';
  std::cout << "fifth:";  for (int& x: fifth)  std::cout << " " << x; std::cout << '\n';
  std::cout << "sixth:";  for (int& x: sixth)  std::cout << " " << x; std::cout << '\n';

  return 0;
}

forward_list constructor examples:
first:
second: 77 77 77
third: 77 77 77
fourth:
fifth: 77 77 77
sixth: 3 52 25 90

Complexity

Iterator validity

Data races

Exception safety

See also

forward_list::operator=

Assign content (public member function )

forward_list::assign

Assign content (public member function )

forward_list::resize

Change size (public member function )

forward_list::clear

Clear content (public member function )